Nitrogen transformations and ammonia loss following injection and surface application of pig slurry:: a laboratory experiment using slurry labelled with 15N-ammonium

A laboratory experiment was designed to determine the fate of N-15-labelled slurry ammonium ((NH4)-N-15-N) and compare soil inorganic-N distribution following surface applied or injected pig slurry. A system of cylindrical volatilization chambers equipped to allow continuous trapping of ammonia (NH3) was used. Undisturbed soil columns were placed in the chambers prior to the application of slurry. A nitrogen balance including soil, air and plant analysis was established for both treatments, 8 days after application. Average cumulative emissions of NH3, were 15% and 11% of the total ammoniacal-N added with the surface and injected treatments, respectively. After 8 days 55% of the (NH4)-N-15-N applied through slurry injection was recovered in the soil inorganic-N pool: 37% as (NH4)-N-15-N and 18% as (NO4)-N-15-N. These figures compare with only 25% N-15-NH4 recovered with the surface applied slurry treatment: 7% as (NH4)-N-15-N and 17% as (NO4)-N-15-N. Immobilization into soil organic-N accounted for 8% of the (NH4)-N-15-N applied for the injected treatment and 6% of the surface applied slurry-N-15. N-15 uptake by the grass was 2% and 7% for the injected and surface applied treatments, respectively. The percentage of added N-15 accounted for was 76% for the injected treatment and 53 % for the surface applied slurry treatment.